Increased utilization is being made of thermoplastic materials in the container industry. For example, several brands of soft drinks are now available in two liter plastic containers. Such containers typically comprise a clear or tinted tubular bottle of polyethylene terephthalate (PET) material, a paper label and a metal cap. The paper label is usually attached to the bottle with a hot melt adhesive, such as ethylene vinyl acetate (EVA) material, and may include a polypropylene coating. The metal cap is typically formed of aluminum. Some containers also include a cup of polyethylene attached to the base of the bottle with hot melt adhesive, while the bottoms of the bottles of other containers are formed in order to be free standing.
Substantial quantities of such containers are produced for consumption, after which it has been common practice to incinerate the user containers or utilize them as land fill. When considering the production scale of the bottling industry, it will also be appreciated that considerable quantities of such contianers are also rejected and discarded during the manufacturing process before filling, distribution and usage. A great deal of useful material is thus being discarded because the technology to recycle it has been either unavailable or uneconomical.
More recently, however, there has been growing interest in recycling plastic beverage containers especially in view of the increasing cost and unavailability of petroleum-based materials along with the expanding applications being developed for PET material in particular. In addition, since several states either have adopted or are considering adoption of legislation requiring deposits on all beverage containers, it is expected that even more plastic containers will be readily available for recycling.
The Goodyear Tire and Rubber Company, for example, has developed a system for processing plastic containers into a usable form of PET. After collection, the used or rejected plastic bottles are first densified by compaction or grinding to reduce their bulk. The densified material is then transported to a recycle facility for separation into its discrete components. The paper particles, which are lightest, are first separated by fluidization in an air separator, after which the heavy fraction is gravity fed into an eddy-current separator for removal of aluminum and other nonferrous metals. The process stream, which at this point comprises mainly PET and polyethylne with traces of miscellaneous materials, in then conveyed into hydraulic separators for removal of materials having specific gravities different from PET. After hydraulic separation, the remaining traces of paper and adhesives are removed from the PET in washers before the recycled PET product is dried. The Goodyear system, however, in unduly complex and expensive, and suffers from the disadvantage of low production capacity.
There is thus a need for a new and improved system for separating plastic bottles into their discrete components for recycling.